Fire detector installation and support bracket therefor



July 10, 1962 .1. E. LINDBERG, JR 3,043,545

FIRE DETECTOR INSTALLATION AND SUPPORT BRACKET THEREFOR 4 Sheets-Sheet 1Filed Aug. 10, 1959 INVENTOR. JOHN E. L/NDBERG, JR.

July 10, 1962 J. E. LINDBERG, JR 3,043,545

FIRE DETECTOR INSTALLATION AND SUPPORT BRACKET THEREFOR Filed Aug. 10,1959 4 Sheets-Sheet 3 & L i .Q@

FIG. 12

L (Am F). HG- I 70 INVENTOR. JOHN f. [.INDBERG, JP.

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ATTORNEY July 10, 1962 J. E. LINDBERG, JR 45 FIRE DETECTOR INSTALLATIONAND SUPPORT BRACKET THEREFOR Filed Aug. 10, 1959 4 Sheets-Sheet 4 F26- I9 F26- 20 INVENTOR. JOHN E. [/NDBERG, Jp,

BY QM (M- ZITI'ORAZE'Y tures.

United States Patent 3,043,545 FIRE DETETOR INSTALLATIGN AND SUPPORTBRACKET THEREFOR John E. Lindberg, Ir., 32% Springhill Road, Lafayette,Calif. Filed Aug. 14), 1959, Ser. No. 832,771 13 Claims. (Cl. 248--49)This invention relates to an improved fire-detector installation and toan improved bracket for use therein and generally for supportingfilamentary devices, especially long, flexible wires and tubes, such ascontinuous-type sensing elements for fire-detectors of the type used onaircraft.

Conventional supporting brackets for wires and tubes have provenunsatisfactory for use with continuous-type aircraft fire detectors.Such detectors include long, slender, somewhat flexible tubular orwire-type sensing elements which are supported in a zone undersurveillance and actuate an alarm when the temperature of any portion ofany sensing element exceeds a certain critical level defined by therequirements of the installation. To enable rapid detection of the fire,substantially the entire length of the sensing element must be exposedinstead of being encased or shielded by support devices; so the supportdevices must be short and spaced well apart from each other. The sensingelement must be removable for testing and for replacement; so thesupport devices must enable such removal, and the easier the removal andreplacement are, the better. In addition, the support devices must belight in weight and easy to install.

Heretofore, installations have used clamps with snaps or spring clipsthat held the sensing element in place. With such clamps, each supportpoint had to be accessible so that it could be unclamped when thesensing element was removed and replaced. Since each support point hadto be reached when the elements were being changed, cowling and otherparts of the aircraft had to be removed to give access. When suchbrackets were used, the use of long, one-piece sensing elements wasunduly expensive and cumbersome, and it became the usual practice tojoin a series of comparatively short-length sensing elements end to end,using suitable couplers. Some types of sensing elements do not lendthemselves to such coupling; so the shortcomings in the support bracketsprevented the use of such types of fire-detection equipment. One objectof the present invention is to make practical the use of continuous,long, sensing elements.

Rendering long sensing elements practical is important, for thedetectors made by joining short-length sensors together have provenunsatisfactory. For example, difficulties occurred in continuous-typefire detectors utilizing a change in the electrical characteristics ofthe sensing element that resulted from exposure to flame tempera- Withsuch detector-s, the couplers for the short lengths had to includeelectrical contacts. The sensing elements were usually of highimpedance, and even a small amount of moisture between the contactscaused failure of the system, especially when the moisture containeddissolved salts, as was often the case with transoceanic and marineaircraft. Attempts to seal the connectors hermetically against moistureinvasion were neither satisfactory nor consistent with easy removal ofthe sensing-element sections. Insulating fluids such as silicone jellyhave been inserted into the fittings to try to prevent moisture fromentering and causing trouble, but this approach has also provedunsatisfactory.

Another difficulty with sensing systems employing couplers was that, inmost cases, the weight of the couplers had to be supported entirely bythe sensing element, for if the brackets supported the couplers, theycould not be disconnected easily. The weight of the coupler produced anadditional stress concentration on the sensing element at the pointwhere it entered the coupler, and this stress concentration was furtherincreased when vibration caused motion of the coupler and subsequentflexing of the sensing element. A frequent result was failure of thesystem.

The present invention avoids all the shortcomings of these olderpractices. Indefinitely long sensing elements may be used; so nofittings or connectors are required. After the initial installation ofthe support brackets, access is required only at the two ends of thelong element, which can be close together if the overall route of theelement is a loop. The support brackets of this invention are preferably permanently attached to the structure, for no access to them isrequired in order to free the sensing element. The installation andchanging of elements is therefore fast, easy, and economical.

Other objects and advantages of the invention will appear from thefollowing description of some preferred embodi'ments thereof.

In the drawings:

FIG. 1 is a view in perspective of a support bracket embodying theprinciples of the invention, shown supporting a filamentary device,whose ends have been broken off to conserve space. A portion of thebracket is broken away and shown in section.

FIG. 2 is a View in side elevation of the device of FIG. 1.

FIG. 3 is a view in end elevation and in section, taken along the line3-3 in FIG. 2.

FIG. 4 is a top plan diagrammatic view of an installation of acontinuous filamentary device using a series of the supporting bracketsof the type shown in FIGS. 1-3.

FIGS. 57 are fragmentary views in perspective, showing the attachment ofa tube to a draw-wire as used in the method of this invention. FIG. 5shows the ends of the tube and draw-wire before insertion; FIG. 6, theinsertion; and FIG. 7, the crimped securement.

FIG. 8 is a view in side elevation showing the end securement of thedraw-wire.

FIG. 9 is a top plan view of two brackets with the filamentary devicecurved between them and a triangle used in making such an installation.

FIGS. 10-12 are views in perspective show-ing the detachment of an olddraw-wire and the attachment of a new one used during replacement of asensing element. FIG. 10 shows a scored sensing element, FIG. 11 abroken-off connection, and FIG. 12 the attachment of the new draw-wire.

FIGS. 13 and '14 are fragmentary views in perspective, showing amodified form of attachment of a draw-wire the same size as the tube,but with an end of reduced diameter, FIG. 13 showing the members apartand FIG. 14 showing them joined together.

FIG. 15 is a fragmentary view in perspective of a brazed juncture of afilamentary device to a draw-wire of the same diameter.

FIGS. 1618 are fragmentary views in perspective of a sleeve-typeconnection between a filamentary device and a draw-wire, FIG. 16 showingthe three elements before insertion, FIG. 17 showing them afterinsertion, and FIG. 18 showing them crimped together.

FIG. 19 is a view in side elevation of a modified form of bracket forsupporting three filamentary elements, the ends of the elements beingbroken oif to conserve space.

FIG. 20 is a view in end elevation of the bracket of FIG. 19.

FIG. 21 is a view in side elevation of a modified form of bracketgenerally like that of FIG. 20.

FIG. 22 is a view in end elevation of the bracket of FIG. 21.

FIG. 23 is a view in perspective of another modified form of bracketassembly.

The bracket 39 of FIG. 1 may be made from sheet stock of any metalsuitable to the application, spotwelded at a web 31 and shaped toprovide a cylindrical sleeve 32. The bracket 36 is spread apart belowthe web 31 at angularly extending portions 33 and 34 and bent at theends to form bases 35 and 36. The bases 35 and 36 are preferably punchedwith holes 37 to receive screws, rivets, or other fastening members 38(FIG. 8) by which the bases 35 and 36 are secured to a supportingstructure 39, such as an engine housing. Alternatively, the bases 35 and36 may be welded in place.

The bracket 30 also includes a suitable plastic bushing 4%), which isput in place in the sleeve 32 before the web 31 is welded together.Preferably, the bushing 40 is made from polytetrafluoroethylene (e.g.,Teflon), which has an extremely low coeflicient of sliding frictionagainst smooth metal surfaces. The tubular body 41 of the bushing 46 isof substantially the same diameter as the inside of the sleeve 32 andfits snugly within it. Enlarged portions 42 and 43 at the ends of thebody 41 engage the sleeve 32 and prevent the bushing 40- from slippingout or being pulled out of the sleeve 32. There are also extensions ornipples 44, 45 at each end. A longitudinal hole 46 in the bushing 40slida-bly receives the sensing element 50, or other filamentary device.

The nipples 44 and 45 provide a controlled degree of stiffness to dampout vibratory motion of the sensing element t) and thus reduce theconcentration in the sensing element 50 of high, localized stresses dueto vibratory motion. If the structure 39, to which the support bracketsare aflixed, executes vibratory motion, this motion is transferred tothe device 50 mounted on the brackets 30. Due to the mass of the device50, however, its motion will not be exactly the same as that of thebrackets 30 and therefore the device 50 will be subject to flexing,concentrated largely at the points where the device 50 enters thebushing 40. If the bushings are rigid at these points, then all of theflexure of the device 50 will be concentrated in a very limited regionof the device and may significantly shorten the lifetime of the device.The extensions 44 and provide flexible support for the device at thispoint, so that any vibratory motion is spread out over the relativelylong segments of the device, in the extensions thus reducing the stressconcentration. In addition, the flexible plastic material imparts to theextensions 44, 45 some degree of damping to the vibratory motion of thedevice 50 with respect to the brackets 30,

further reducing the stress concentration at the points where the deviceenters the bushings.

The extensions 44 and 45 also are stiff enough to prevent the device 50from being bent in a sharp corner at the point where it enters thebushing (see FIG. 8). Instead, the extensions 44, 45 provide a definiteradius of curvature through which the device 50 is bent. This feature isespecially valuable for installations which require the device to be runover a complicated, crooked route.

The bracket assemblies are preferably installed permanently in theaircraft, being spaced at suitable intervals, which depend upon theradius of the are through which the sensing element 50 is bent. Thespacing of the brack et assemblies must, in general, be decreased as thebend radius decreases. FIG. 4 shows several bracket assemblies 30mounted in a hypothetical pattern, the length of the brackets 30 beingexaggerated somewhat.

After the bracket assemblies 30 have been installed, a smooth, strong,flexible draw-wire 51 is threaded through the bushings 40, following theplanned path of the sensing element 50. This draw-wire 51 is fastened tothe end of the sensing element 50 by some convenient means. FIGS. 5-7show one such means, wherein the draw-wire 51 is first inserted asuitable distance, e.g., one-half inch, into a tubular sensing element50, and then the tube is crimped onto the draw-wire 51 by a suitablecrimping tool, producing the crimps 52, 53, and 54. In any event, thedraw-wire 51. is joined to the sensing element 50 in such a manner thatthe juncture will pass smoothly and easily through the bushings 46.Thus, the juncture should not result in an enlarged knob.

The sensing element 5% is then pulled by the draw-wire 51 through thebushings 449. When the element 59 is in the proper position, as shown inFIG. 8, the draw-wire 51 may be tied to some steady point nearby, forexample the next-to-the-last mounting bracket 39, and the excess lengthof draw-Wire is clipped off. The tie provides a slight constant tensionon the sensing element which keeps it in place without slipping. Theinstallation of the sensing element is completed with this step.Connection between the element 50 and the other elements of the firedetector or other device with which it is used are standard and need notbe shown here.

Occasionally, for example, when using a very long sensing element orwhen running the element over a very complicated path, it may be foundthat a small amount of lubrication assists the installation of theelement 56. In this event, any common type of fluid lubricant, such asengine oil, may be used. The lubricant may be satisfactorily applied bymeans of a rag soaked in the lubricant, the rag being used to wipe thesensing element as it is being drawn into place in the bracketassemblies.

There is a maximum angle A through which the sensing element 50 may bebent between two support bracket assemblies 30 and still slip easily andproperly through the bushings 40. This angle A depends upon the strengthand stiffness of the particular element 54 For any particular material,this invention provides an installation aid, comprising an isoscelestriangle 60 preferably made of sheet metal and laid out as shown in FIG.9, with the angle B at its vertex 61 equal to 180 minus A. The sides 62,63 of the triangle 60 are marked in terms of bend radius, as calculatedfrom the angle A, starting with zero at the vertex 61 and increasing inboth directions along the sides 62 and 63.

The triangle 60 is used as follows. One side 62 is placed against thelatest-installed support bracket assembly 30 opposite the numbercorresponding to the desired bend radius. The next bracket assembly 30is then held against the other side 63 of the triangle 60 opposite thesame number. This procedure gives the correct position for the nextbracket assembly 30. Note that the center of curvature 64 of the path 65of the sensing element 50 lies at the intersection of the perpendiculars66, 67 from the two bracket assemblies. The bend radius is the distancefrom the center of curvature 64 to either of the brackets. The bracketassemblies 30 are installed one by one in this way, with the trianglealways giving the correct spacing and orientation for any chosen bendradius.

When it is desired to replace the device, the old drawwire 51 is removedas shown in FIGS. 1012 by scoring the tube 50 at 55 (FIG. 10) andbreaking it there (FIG. 11) just beyond the end 51a of the old wire 51,thus exposing an open end 56 of the tube 50. A new draw wire 57 may thenbe fastened to the device by crimps 58 and 59 (FIG. 12) and is pulledinto place along the route as the device 50 is pulled out. Thisprocedure leaves the draw-wire 57 in place for the subsequentinstallation of a new device 50, if desired, either immediately or at afuture time.

Where there is a possibility that the point at which the draw-wire 51 isfastened to the device might catch on the edges of the holes 46 in thesupport-bracket bushings 40 and hinder the proper drawing into place ofthe device, this possibility can be eliminated by using a draw-wire 70of the same diameter as the device 50, as shown in FIGS. 13 and 14, andreducing the diameter of the wire 70 at an end portion 71, so that itwill fit into the open end of the device, where it can be secured bycrimps 72 and 73, thereby providing a joint with a smooth juncture 74.

The use of the draw-wire is not, of course, limited to devices in theform of open-ended tubes. A draw-wire 75 may, for example, bebutt-welded, either by brazing or by electric welding, to the end of asolid device 76, giving a smooth joint 77, as shown in FIG. 15.

A means of fastening a draw-wire 80 to a solid device 81 by means of asleeve 82 is shown in FIGS. 16-18. Here, reduced end portions 83 and 84are provided in the Wire 80 and device 81, respectively, and the ends 83and 84 are inserted in the tubular opening 85 in the sleeve 82. Thesleeve 82, wire 80, and device 81 all have the same outside diameter.Crimps 86, 87 complete the juncture.

An additional variation of this general scheme is to use, instead of thedraw-wire described above, a drawtube for pulling the device into place.This tube can be slipped over the end of the device and crimped downthere, or can be joined by a nipple. The passages 46 in thesupport-bracket bushings 40 naturally have to be large enough for thedraw-tube to pass through them, but no difficulty can be encounteredfrom the joints catching on the edges of the holes, because asmall-diameter section follows a larger-diameter section as the jointpasses each support bracket If desired, the end of the device to bemounted can be reduced in diameter so that it will fit inside adraw-tube of the same outside diameter as the device.

The methods just outlined for attaching the drawwire or draw-tube to thedevice to be mounted are primarily intended to be used in cases wherethe device is metallic, so that the techniques of crimping and brazingare applicable. However, it is by no means necessary that the use ofthese support brackets be limited to supporting metallic devices.Flexible plastic or rubber tubes or rods can easily be attached to thedraw-wire by means of suitable cement, such as epoxy resins. Endlessvariations will no doubt suggest themselves to anyone interested in theuse of this invention, without departing from the principles embodiedtherein.

The application of this invention is not limited to use with aircraftfire detectors, although very useful therewith. Any device which islong, thin, and flexible can suitably be supported by using thisinvention, and the invention will be particularly suitable if the deviceneeds to be replaced more or less frequently. Examples of such devicesmight be electrical wires, tubing, and control wires for transmittingmotion.

This invention would prove especially useful for supporting electricalwires when it is expected that frequent rerouting of the wires will benecessary. There is no restriction to the number of wires which might beplaced in one bushingas is exemplified by FIGS. 19 and 20, where threewires 90, 91, and 92 are carried by each bracket assembly 93. Itsbushing 94 is simply made large enough and is provided with one hole foreach wire. The ease and speed with which the wires could be inserted andwithdrawn are apparent from the foregoing discussion. In addition, thebrackets 93 make it quite feasible to avoid the use of insulated wire byproper design of the bushings 94 so that the physical spacing of thewires is preserved. Thus, not only are short circuits between therespective wires prevented, but the characteristic impedance betweenpairs of wires is maintained, so they can be used for transmittingalternating current. The dielectric properties ofpolytetrafluoroethylene are quite good, and short circuits to ground aretherefore prevented.

FIGS, 21 and 22 show another form of bracket assembly 95 for supportingmore than one device in each support bracket. Again, each wire 90, 91and 92 is supported in its own hole in a bushing 96. For someinstallations, no extensions are needed on the bushing, becausevibration is no problem. The bushing 96 omits the extensions, toillustrate this fact.

By means of this invention, control wires which transmit motion toactuate mechanical devices may be run over quite complicated routes. Thelow friction between the control wires and the bracket bushings helps tomaintain high efficiency in the control system.

The convenience with which the component supported with this inventionis installed and removed is useful in installations of flexible tubing,either metallic or nonmetallic, for fluid or gas transfer, especiallywhen such installations require occasional re-routing of the tubing. Theself-lubricating property of the bushing material makes it unnecessaryto provide any other lubricant to reduce the friction between the tubingand the bushings when installing or removing lengths of the tubing.

FIG. 23 shows an assembly molded from one piece of Teflon. It has atubular opening 101 in a bushing-like portion 102, and a bracket portion103, generally triangular in cross section with a reces 104 and openings105 on each side to receive suitable screws or other fastening means.Operation is the same as before.

To those skilled in the art to which this invention relates, manychanges in construction and widely differing embodiments andapplications of the invention will suggest themselves without departingfrom the spirit and scope of the invention. The disclosures and thedescription herein are purely illustrative and are not intended to be inany sense limiting.

I claim:

1. A support assembly for a fire-detector sensing element of thecontinuous unitary type, comprising: a onepiece metal bracket having acylindrical sleeve, a web closing said sleeve axially thereof, andsupport legs for said web; and a one-piece unsplit tubular bushingsnugly filling said sleeve and having enlarged portions at each end ofsaid sleeve locking said bushing against sliding movement relative tosaid sleeve and having flexible extensions of reduced diameterprojecting beyond said enlarged potrions, to aid in damping vibrationstransmitted through said assembly to said sensing element, said bushingbeing made of flexible material having a low coeflicient of slidingfriction and providing at least one seamless circumferentially fullyclosed through cylindrical passage of constant bore, so that saidsensing element of substantially the same diameter as said passage canbe pulled therethrough without loosening said bracket.

2. A fire detector installation, including in combination: an elongated,substantially filamentary, continuous, one-piece, unjointecl, somewhatflexible sensing element; a filamentary draw-element secured to one endof said sensing element; and a plurality of support means spaced apartfrom each other to describe a path, said support means supporting saidsensing element and each comprising a support bracket and a one-piecetubular bushing supported by said bracket and having a seamlesscircumferentially fully closed smooth cylindrical opening at least aslarge as said sensing element extending longitudinally therethrough anda low coefficient of sliding friction, said draw-element being used tobe pulled through said openings of said bushings for pulling saidsensing elements thereafter into a position where they are all supportedby said support means,

3. The installation of claim 2 wherein said bushing is made frompolytetrafluo-roethylene.

4. The installation of claim 2 wherein said drawelement is a wiresmaller in diameter than said sensing element, said sensing elementbeing a tube crimped to said draw-wire.

5. The installation of claim 2 wherein said drawelement is the samediameter as said sensing element.

6. The installation of claim 5 wherein said drawelement has an end ofreduced diameter and said sensing element is tubular, said draw-elementreduced end being fully inserted in said sensing element and saidsensing element crimped to said reduced end,

7. The installation of claim 5 wherein said drawelement and said sensingelement are butt-welded to gether.

8. The installation of claim 5 wherein both said drawelement and saidsensing element have ends of reduced diameter, and a sleeve crimped tosaid ends, said ends being fully inserted in said sleeves.

9. The installation of claim 2 wherein there is anchor means near thelast said support means and at the end of said path said draw-element isbrought around and tied to said anchor means to place tension on saidelement.

10. The installation of claim 9, wherein said anchor means includes thenext-to-last said support means.

11. A fire detector installation, including in combination: anelongated, substantially filamentary, continuous, one-piece, unjointed,somewhat flexible sensing element; a draw element secured to one end ofsaid sensing element; and a plurality of support elements supportingsaid sensing element and spaced apart from each other to describe adesired path, each said support element including a support bracket anda one-piece tubular bushing supported by said bracket and having aseamless circumferentially fully closed smooth cylindrical opening ofsubstantially the same diameter as said sensing element, saiddraw-element being used by being pulled through said support elements topull said sensing element thereafter.

12. A fire detector installation, including in combination: anelongated, substantially filamentary, continuous, somewhat flexiblesensing element; a draw-wire; means securing said draw-wire to one endof said sensing element by a joint no larger in diameter than saidsensing element; and a plurality of support assemblies spaced apart fromeach other to describe a path, said assemblies supporting said flexiblesensing element and each comprising a suppont bracket having a sleeveand a one-piece tubular low-friction-plastic bushing snugly fitting insaid sleeve and having enlarged portions engaging the ends of saidsleeve and extensions of reduced diameter extending t beyond saidenlarged portions and a seam-less circumferentially fully closed openingat least as large as said sensing element extending longitudinallytherethrough, said draw-wire being used to be pulled through saidopenings of said bushings for pulling said sensing elements thereafter.

13. A fire detector installation, including in combination: anelongated, substantially filamentary, continuous, one-piece, unjointed,somewhat flexible sensing element; a draw wire secured to one end ofsaid sensing element; and a plurality of support assemblies spaced apartfrom each other to describe a looped path with the first and last onesclose together, said assemblies supporting said sensing element and eachcomprising a metal support bracket having a cylindrical sleeve and aone-piece tubular plastic bushing snugly fitting in said sleeve andhaving enlarged portions engaging the ends of said sleeve and extensionsof reduced diameter extending beyond said enlarged portions and aseamless circumferentially fully closed opening at least as large assaid sensing element extending longitudinally therethrough, saiddraw-wire being used to be pulled through said openings of said bushingsfor pulling said sensing elements thereafter, said plastic having a lowcoefficient of sliding friction.

References Cited in the file of this patent UNITED STATES PATENTS416,284 Adams Dec. 3, 1889 770,278 Fletcher Sept. 20, 1904 973,311 SmithOct. 18, 1910 1,190,971 Williams July 11, 1916 1,610,196 Blaisdell Dec.7, 1926 1,744,190 Wilson Jan. 21, 1930 1,759,794 McDade May 20, 19302,240,330 Flagg et al. Apr. 29, 1941 2,631,819 Duncan Mar. 17, 19532,683,578 Rainey July 13, 1954 2,858,106 Anton Oct. 28, 1958 2,882,547Bacon Apr. 21, 1959 2,882,952 Johnson Apr. 21, 1959 FOREIGN PATENTS369,922 Great Britain Mar. 15, 1932 722,083 Great Britain Jan. 19, 1955

